A muffler is a device for reducing the amount of noise emitted by a machine. On internal
combustion engines, the engine exhaust blows out through the muffler. The
internal combustion engine muffler or silencer was developed in parallel with
the firearm suppressor by Hiram Percy Maxim.

Mufflers are typically
installed along the exhaust pipe as part of the exhaust system of an internal
combustion engine (of a vehicle, or stationary) to reduce its exhaust noise.
The muffler accomplishes this with a resonating chamber, which is specifically
tuned to cause destructive interference, where opposite sound waves cancel each
other out.

Catalytic converters also often have a muffling effect.
The effect is mainly generated largely by restriction, rather than by cancellation.

Mufflers
that reduced backpressure relative to earlier models became
increasingly available in the late 20th century, and resulted in increased
engine efficiency, performance, power output, and simultaneously decreased overall
wear and tear on the engines' components, as well as sound to levels in compliance
with the law.